2. What is it and how to use it?

Have you ever developed XML applications using XSLT? If so you probably
felt the need of viewing the result of applying the XSLT processor on
the XML file using an XSLT sheet you have been working on right inside
your (X)Emacs, without having to go to a terminal or to the Web
browser. This minor mode allows you to do it!

The XSLT-process minor mode allows you, while you're inside a
buffer for which this minor mode is enabled, to enter a few keystrokes
that will invoke the XSLT processor of choice on the buffer. The result
is displayed in another (X)Emacs buffer, that allows you to quickly
view and inspect the results.

The XSLT file that's used to process the file should be specified inside
the XML file using the XML processing instruction `xml-stylesheet',
like this:

<?xml-stylesheet href="URL/to/XSLT/file" type="text/xsl"?>

You can use any URI understood by your Java system, e.g. file, HTTP or
FTP, to refer to a stylesheet. The XSLT engine will download the
stylesheet from the remote location and make use of it locally. With the
TrAX interface (see section 3.1 Supported XSLT processors), the stylesheet is
cached in the processor, so further invocations of the XSLT processor
won't process the stylesheet again, unless the stylesheet is modified.

You can use URLs which are relative to the location of your XML file.
For example if you have an XSLT file `page-html.xsl' in the same
directory as the XML file you can simply have inside the XML file the
following processing instruction:

<?xml-stylesheet href="page-html.xsl" type="text/xsl"?>

The XSLT-process mode was designed to work with any XSLT
processor written in the Java language. Support for processors written
in programming languages other than Java may require some work.